The present invention relates to automatic machine tools, and more particularly, to an undercutter attachment for an automatic lathe.
In machine shop operations, the maximum utilization of an automatic machine tool is a goal that is being continuously sought. One machine tool can be very useful to a manufacturing operation if that machine tool can efficiently manufacture several different parts, such as parts that are similar but of different dimensions. For this purpose, there have in the past been provided numerous adjustments and attachments for machine tools to give the manufacturer of metal products the maximum use of a machine tool.
One of the best known approaches in extending the usefulness of a machine tool, such as a lathe, is to provide a turret having a plurality of toolholders that are programmed to engage the rotating workpiece at different times during the machining sequence. As machining operations become more and more complex and intricate, it has become the usual thing for every tool position on the turret to be occupied to perform a function during a sequence. If the piece is not completely machined by the time all of the tool stations are expended, then the tool must be run through a second sequence of operations on the same or a different machine tool, which adds considerably to the cost of manufacture of the part.
In addition to the turret mounted tools, modern day automatic machine tools have additional toolholders mounted on cross slides. These additional tools are designed to perform minor machining operations. The tools mounted on the cross slides can perform undercutting operations that heretofore the tools mounted on the turret stations could not.
An undercutting operation is where a portion of the workpiece adjacent the holding chuck is machined to a diameter less than another diameter toward the distal end of the tool. In other words, a cut is made with a larger diameter section between the end of the workpiece and the position of the cut.
The cross slide is ideal for this type of operation since the cross slide can move the tool radially directly into the workpiece when the workpiece has reached the position for starting, as previously programmed. However, there has existed a definite disadvantage in that the cross slides do not move along the workpiece in the axial direction, but instead are stationary. Thus the width of the undercut made by the tools on the cross slides is limited to the width of the tool itself.
When an extended undercut is made, the prior solution on the usual machine tool was to simply use several cutting operations performed by the cross slides. This is a very slow and tedious process, and thus time consuming and costly to the manufacturing operation. Also, the tendency is to employ a tool that is too wide, thereby causing chatter of the tool and an inferior machined surface.
In the prior art, the Bechler U.S. Pat. No. 3,308,693, issued Mar. 14, 1967, is exemplary of the type of approach that has been taken in attempts to extend the capability of an automatic lathe. In this prior art, the tools are mounted on slides that extend into and out of engagement with the work and perform a single location cutting operation. A pair of tools is taught mounted on a single cross slide, but the extent along the length of the workpiece that can be cut by a single tool is limited to the width of the tool. If more cutting is needed, it appears that the answer in the Bechler patent is simply to provide more than one tool mounted on each cross slide at different axial locations.
A different approach is shown in the patent to Poorman, U.S. Pat. No. 3,062,080 in which an undercutting tool is mounted on one station of a turret toolholder. In this arrangement, the length of the undercut that can be made is still limited to the width of the tool that is employed.
Thus, I found it to be desirable to invent an apparatus and method for performing an undercutting operation that is not limited to the width of the tool. I employ a conventional narrow, pointed tool and feeding of the tool relative to the workpiece. The tool is tripped into and out of engagement at the appropriate points along the workpiece. The advantages are: (1) elimination of several tools needed for a single undercutting job; (2) the elimination of chatter and poorly machined parts due to the selection of a tool that is too wide; (3) elimination of the need for several machining sequences to provide one extended undercut portion; and (4) freeing up of the turret stations and cross slides for other machining operations that may be necessary on the workpiece.